From d5f6cbb263662af585b866481382c3f5ba5cd638 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 27 Jun 2024 20:12:44 +0200 Subject: [PATCH] block-copy: Fix missing graph lock The graph lock needs to be held when calling bdrv_co_pdiscard(). Fix block_copy_task_entry() to take it for the call. WITH_GRAPH_RDLOCK_GUARD() was implemented in a weak way because of limitations in clang's Thread Safety Analysis at the time, so that it only asserts that the lock is held (which allows calling functions that require the lock), but we never deal with the unlocking (so even after the scope of the guard, the compiler assumes that the lock is still held). This is why the compiler didn't catch this locking error. Signed-off-by: Kevin Wolf Message-ID: <20240627181245.281403-2-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/block-copy.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/block-copy.c b/block/block-copy.c index 7e3b3785282..cc618e45614 100644 --- a/block/block-copy.c +++ b/block/block-copy.c @@ -595,7 +595,9 @@ static coroutine_fn int block_copy_task_entry(AioTask *task) if (s->discard_source && ret == 0) { int64_t nbytes = MIN(t->req.offset + t->req.bytes, s->len) - t->req.offset; - bdrv_co_pdiscard(s->source, t->req.offset, nbytes); + WITH_GRAPH_RDLOCK_GUARD() { + bdrv_co_pdiscard(s->source, t->req.offset, nbytes); + } } return ret; -- 2.39.5